Voltage regulating system



R. R. JOHNSON VOLTAGE REGULATING SYSTEM Filed Sept. 14, 1959 Dec. 5,1961 Smwm oom+ l 1. NN

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UnitedStates Patent O 3,012,187 VOLTAGE REGULATING SYSTEM Robert R.Johnson, Menlo Park, Calif., assigner, by mesne assignments, to theUnited States of America as represented by the Secretary of the NavyFiled Sept. 14, 1959, Ser. No. 839,983 2 Claims. (Cl. 323-56) Thepresent invention relates in general to voltage regulators, and moreparticularly .to a regulating device, incorporating a magneticamplifier, which is effective to develop an essentially constant outputpotential regardless of random iluctuations in supply line voltage.

In some types of electronic equipment, it is highly desirable to haveavailable -an unv-arying voltage which can be applied, for example, to avacuum tube heater circuit in cases where signal ouput from theapparatus is critically dependent upon the avoidance of variations incathode emission resulting from random heater voltage liuctuations. Suchheater voltage irregularities can change the gain of the tubes, or bringabout a shift in the point at which they operate on their characteristiccurves. Although equipment of the nature referred to is frequentlyprovided with a regulated power supply for the tube plates or anodes, itis not usually practicable to bleed energy from this source -for heaterpurposes since the complexity and/ or weight of such an anode powersupply is markedly increasedk by lthe heavy current drain thus imposedthereon.

The present invention yovercomes this difficulty by utilizing energydirect from the power line, and then provides means to compensate for`any fluctuations in Iline supply. This means includes a magneticamplifier controlled from a pair of balanced vacuum tubes, the latterbeing biased in accordance with the algebraic sum of the voltagesrespectively derived from the regulated power supplyand from the poweryline input. Any change in the value of this bias, resulting from apower line Variation, unbalances the vacuum tubes, and results in thedevelopment of an electromagnetic flux to partially saturate the core ofthe magnetic amplifier. This has the effect of altering the value of theamplifiers output as compared to the input thereto, and such output, inproper polarity and phase, is fed back to the heater trans-former toneutralize the power line fluctuations.

' One object of the present invention, therefore, is to provide 4animproved form of electronic voltage regulator actingto compensate forrandom irregularities in energy received from a supply line.

- lAnother object ofthe invention is to provide a voltage regulator, ofthe type described, incorporating a magnetic amplifier which acts todevelop a control variation of such polarity and phase as to neutralizeinput fiuctuations which would otherwise appear in the output of theapparatus.

Other objects and many of the attendantadvantages of this invention willbe readily appreciated as the same becomes better understood byreference to the following detailed .description when considered inconnection with the accompanying drawing, the singlegure of which is aschematic representation of a voltage regulating circuit embodying apreferred form of the present invention.

Referring now to the drawing, there is illustrated a transformer,generally identified by the reference numeral 10, which acts in 4theexample chosen to step down a standard A.C. line input of llO-lZO kvoltsto approximately 6 volts for utilization by some such equipment as theheaters of a series of vacuum tube amplifiers in a radar detectionsystem or other similar receiver of radiant energy. The transformer 10has two primary windings `12 and 14 between which a connection is madeat 16 for 3,012,187 Patented Dec. 5, 1961 ice purposes -to be laterdescribed. The line input, a-t approximately volts, is applied towinding 12, this input wave having a frequency which may, for example,be in the neighborhood of 400 cycles per second. As is often the casewith energy taken directly from a general supply source, randomfiuctuations may be ypresent which normally are passed into thetransformer output circuit and are thus received by the utilizationapparatus.

In the system of the drawing, such a utilization apparatus (not shown)is connected to one secondary tr-ansformer winding 18. The latter ismagnetically coupled, as illustrated, to the primary winding 14. Therelative number of turns of each of these windings is so chosen that thevalue of the output energy is approximately 5.8 volts, although thisfigure is obviously predetermined in accordance with the particularoperating requirements of the utilization equipment. Another secondarytransformer winding 20 is lcoupled to the primary winding 12. Fromwinding 20 energy is supplied to the series-connected primary windings22 of a saturable-core transformer acting as a magnetic amplifier. Thislatter is generally identified in the `drawings by the reference numeral24.

The saturable-core transformer 24 includes, in addition to thepreviously-mentioned primary windings 22, a pair of series-connectedsecond-ary windings 26 and a further pair of series-connected controlwindings 28. All three windings 22, 26, and 28 of transformer 24 aredisposed in inductive relationship to one another, and, in accordancewith the well-known operating characteristics of such devices, thetransfer of energy between the primary -and secondary windings 22 and26, respectively, is a function of the degree of saturation of thetransformer core, and the latter in turn is `dependent upon the densityof the magnetic flux developed by current diow in the control windings28. Such flux tends to saturate the transformer core and reduce theoutput of the transformer. Expressed differently, the output of the unit24, as derived from windings 26, is a function both of the energysupplied to the primary windings 22 and the flux developed by currentflow in the control windings 28, these two factors being broadlyeffective in an opposite sense in lthat an increase in the latter tendsto reduce the electromagnetic coupling between the primary and secondarywindings 22 and 26, respectively, and hence precludes an increase ininput energy to windings 22 from being proportionally transferred to thetransformer output.

The voltage appearing at point 16 is rectified by a crystal diode 30.This diode is electrically connected so that the yoltage developed onits associated storage capacitor 32 1s of negative polarity, with thecircuit constants being so chosen that fluctuations in line voltageappearing at point 16 develop corresponding changes in the value of theenergy stored by the capacitor. Such energy is applied to one terminalof a series-connected voltage divider network consisting of tworesistors 34 and 36 and a potentiometer 38. The remaining terminal ofthe voltage divider is connected to a stable source of energy such asthat which supplies operating potential to the anodes of the electrondischarge tubes of the receiver. It is essential thatsuch source beregulated, or otherwise `free from liuctuations, throughout the intervalduring which described system is to be effective. The value of thispotential source connected to resistor 36 (approximately300 volts in theexample given) is such that the movable Contact of potentiometer `38'canbe manually adjusted close to a point of nominally zero voltage, basedupon the magnitude of the energy stored in capacitor 30 under normalline input conditions. This is accomplished when the positive potentialfrom the regulated sourceapproximately equals (at the location of themovable potentiometer terminal) A pair of vacuum tube triodes V1 and V2are arranged y in Abalanced relationship, with the cathodes of the tubesbeing directly connected together and thence to ground through a commonresistor 40. The anode of triode V1 is supplied with energy from theregulated operating po4 tential source through one of the controlwindings 28 ofv the magnetic amplifier 24, While the anode of triode V2is similarly supplied through the remaining control winding, asillustrated in the drawing. The control electrode of triode V2 isgrounded directly, while that of triode V1 is connected to the movablecontact of potentiometer 38.

In describing the operation of the illustrated circuit, it will rst beassumed that the line input is of normal value, thus yielding a desiredconstant voltage output from the transformer secondary winding 1S. Undersuch conditions, the cylically varying voltage appearing at point 16 isrectied lby the diode 30 to develop on capacitor 32 a negative voltageof such magnitude as to lapproximately balance, at the movable contactof potentiometer 218, the positive potential obtained from the regulatedsource 'connected to resistor 36. This is equivalent to stating that thepotential on the control electrode of triode V1 approxi-V mates zerovolts. Since the potential on the control electrode of triode V2 isalways at zero volts (ground), the two tubes are close to being inbalance, and conduct almost equally to cause nearly equal currents toflow through the two control windings 28 of the magnetic amplifier 24.`These two currents are in such directions as to oppose one another,however, and hence'little resultant electromagnetic flux is produced inthe transformer y The core` and only slight saturation of the latteroccurs. input energy, -as it appears across the secondary winding Ztl ofthe heater transformer V1t); is electromagnetically transferred betweenthe primary and secondary windings 22 and 26 of the magnetic amplifier24 and fed back to the point 16 so as to maintainr a predeterminedvoltage drop across Winding 14.

Now, however, assume that an undesired fluctuation occurs in the linesupply, and that the voltage appearing at point 16 rises momentarily asa result thereof. Nominally this Would cause a corresponding increase inthe output energy derived from the transformer secondary winding 18.However, when such a rise occurs, the unidirectional voltage developedon capacitor 32 also arises,

Vand hence the potentiometer voltage at its movable con- 4 It isdesirable to have the voltage on the control electrode of triode V1 onlyapproximate zero in order to allow for uctuations of the line voltage ina negative `as well as in a positive direction. Otherwise tube V1 wouldbe in complete balance with triode V2 under normal voltage conditions,and momentary drops; in line voltage would place a positive potential onthe control electrode of the tube. Its conductive status at such timeswould therefore not be such as to yield the desired compensating action.

Obviously many modifications and variations of the present invention arepossible in the light 'of the above teachings. It is therefore'to beunderstood that within the scope y of the appended claims the inventionmay be practiced partially saturate the core thereof and thereby modifythe y y energy transfer from primary windings 22 `to. secondary windings26. The latter are sowound Ythat the phase vof `the energy fed back topointj16 neutralizes, or compensates for, the yincrease -inline'voltage, tand hence the drop across transformer winding 1 4 remainsconstant reglardlessrof the input fluctuation from which the regulatoryelect was derived. f

otherwise than as specifically described.

I claim:

1. In a regulatory circuit for developing a substantially constantoutput voltage of relatively low amplitude from a cyclically varyinghigher-amplitude bidirectional line input which is subject torandomrfluctuations from a nominal value: the combination of :atransformer having at least one primary winding to which input energyfrom said line is applied, a secondary winding for developing aregulatory control voltage, and a step down secondary winding forderiving said relatively low-amplitude output voltage; a saturable-coremagnetic amplier having primary, secondary, and control windings; aconnection between the regulatory control winding of said transformerand the primary winding of said magnetic amplifier; a feedbackconnection from the secondary winding of said magnetic amplifier to apoint on the yprimary winding of said magnetic amplifier; a feedbackconnection from the -said transformer; means for rectifying at least aportion of the `cyclically-varying input energy; a source of constantpotential of opposite polarity to that developed by said rectifyingmeans; a voltage divider connected betweenV ythe constant potentialsource and the output of said rectifying means; circuit means responsiveto changes yin the voltage appearing at a nominally balanced pointonsaid voltage divider to correspondingly vary the vamountof currentflowing throughout the control windings of .said magnetic amplifier andthereby alter the degree of saturation of said core andfhence thetransfer of .energy between the pirmary and secondary windings of saidamplifier; and means for applying the energy so transferred between .theprimaryand secondary windings of said magnetic ampliiier to'stabilizethe amountV of inductive coupling between theprimary and step downsecondary windings of said. transformer.

2. A regulatory circuit accordingto `claim l in'whicih Vthe circuitmeans responsive to .changes in thevoltage References Cited in the fileof this patent UNITED STATES PATENTS 1,894,133 ThompsQn Jan. 10, 193.31,997,657 `561mm f Apr. 16, 1955 2,743,785 L66 u May 1, 1956 ,2,883,608v smith 'Apr. 21, 195,9 2,920,264

